Beyond the ‘Truth Serum’

Narcoanalysis is often sensationalised as a “truth serum”, but in reality, it is a scientific investigative aid grounded in neuroscience and forensic psychology.

In an era where crime has become increasingly sophisticated, law-enforcement agencies are compelled to rely on science as much as instinct. Among the most debated tools in this scientific arsenal is narcoanalysis, often sensationalised as a “truth serum” test. While critics question its ethics and reliability, narcoanalysis, when applied lawfully and scientifically, has proved to be a valuable investigative aid, particularly in complex and deadlocked cases.

Narcoanalysis involves the controlled administration of barbiturates such as sodium pentothal (sodium thiopental), sodium amytal, or similar drugs that depress the central nervous system. These substances induce a semi-conscious state in which higher cognitive inhibitions are lowered. The scientific premise rests on neuroscience and psychology: when cortical control is suppressed, a subject becomes less guarded, allowing spontaneous verbalisation of memories that may be consciously suppressed during conventional interrogation. Trained forensic psychologists, assisted by anaesthesiologists, conduct questioning in this altered mental state, ensuring medical safety and procedural discipline.

From a neural and philosophical standpoint, narcoanalysis recognises the layered nature of human cognition. Memory is not always accessible through conscious recall; fear, guilt, or trauma often block truthful disclosure. By chemically reducing mental resistance, narcoanalysis can allow access to subconscious recollections.

India’s experience with narcoanalysis includes several high-profile criminal investigations. In the Nithari serial killings case, narcoanalysis of the accused reportedly helped investigators reconstruct timelines and locate corroborative evidence when the probe had reached a standstill. Similarly, during the Telgi fake stamp paper scam, narcoanalysis was used to unravel the scale of the conspiracy and identify critical links, leading to further recoveries and arrests. In cases involving organised crime and terrorism, the technique has often served as a breakthrough mechanism.

The judiciary has acknowledged this investigative utility while firmly drawing constitutional boundaries. In Selvi & Ors. v. State of Karnataka (2010), the Supreme Court held that involuntary narcoanalysis is unconstitutional, as it violates the right against self-incrimination under Article 20(3) and the right to personal liberty under Article 21. However, the judgement did not discard narcoanalysis altogether. Instead, it carved out a lawful space for its voluntary use, subject to strict safeguards.

The Court clarified that narcoanalysis may be conducted only with the free, informed consent of the subject, recorded before a judicial magistrate, with access to legal counsel and full disclosure of medical and legal consequences. Crucially, while statements made during narcoanalysis are not admissible as evidence, the court recognised that facts discovered as a result of such statements may be admissible, provided they are independently verified. Thus, if narcoanalysis leads to the discovery of a weapon, location, or material fact, and such discovery is corroborated independently, it can assume evidentiary value not because of the statement itself, but because of the factual discovery it enables.

Indian courts have, on occasion, acknowledged the relevance of scientific interrogation techniques. The Bombay High Court, in cases such as Ramchandra Ram Reddy v. State of Maharashtra, emphasises narcoanalysis and related forensic tests as necessary modern investigative tools, provided they are conducted ethically, scientifically, and under judicial oversight. While courts remain cautious, there is judicial appreciation of science-led investigation when constitutional safeguards are respected.

Institutions such as the Directorate of Forensic Science Services (DFS) and Gujarat FSL have further strengthened the credibility of narcoanalysis by developing it within a forensic psychology framework, adhering to international medical and ethical standards. Their work demonstrates that narcoanalysis, when conducted by experts rather than interrogators, can align with both science and law.

Narcoanalysis is neither a magic wand nor a mediaeval coercive practice. It is a scientific investigative aid, meant to supplement—not supplant—traditional evidence. Used voluntarily, cautiously, and professionally, it can illuminate investigative paths otherwise hidden. In the balance between civil liberties and societal interest in justice, narcoanalysis deserves not dismissal but disciplined acceptance within the rule of law.

(Kumar is a former IPS officer and forensic consultant to Assam government. Reddy is Forensic Psychologist & Corporate Security & Loss Prevention Executive. Views personal.)